Biomechanical comparison of pin and nitinol bone staple fixation to pin and tension band wire fixation for the stabilization of canine olecranon osteotomies

The history of orthopaedic use of nitinol compression staples

INTRODUCTION

The use of nitinol continuous compression staples has shown clinical utility in the management of various orthopaedic injuries. While literature is most robust in the realm of foot/ankle and spine surgery, the use of nitinol staples has been documented in fixation of wrist, olecranon, patella, and pelvis fractures.

METHODOLOGY

A narrative review was conducted by searching three online databases - PubMed, Web of Science, and Cochrane using the terms "Nitinol" and "Staple" published between 2003 and 2023. A total of 42 articles met inclusion/exclusion criteria and were included in this review.

REVIEW

Literature outside of foot/ankle and spine surgery is largely limited to biomechanical studies, case reports, and finite element analyses. The literature is summarized within this review by anatomic location including foot/ankle, lower extremity, hand, upper extremity, spine, and pelvis.

CONCLUSION

Existing literature demonstrates a diverse array of applications for nitinol continuous compression staples in both axial and appendicular orthopaedic care. Advantages of these implants include ease of application, ability to capture small bony fragments, continuous compression across a fracture or arthrodesis, and full coaptation which maximizes the surface area for healing and/or fusion.

Biomechanical comparison of continuous compression implants versus tension band fixation for transverse olecranon fractures

Purpose

Tension band wiring (TBW) is considered the 'gold standard' for fixation of transverse olecranon fractures (OTA/AO 2U1B1d). However, this approach requires a large exposure, can be technically demanding and operator-dependent, and is associated with hardware prominence. Continuous compression implants (CCI) may address these limitations. To the authors' knowledge, a comparison between TBW and CCI has not been performed. Therefore, this study was designed to compare biomechanical properties of CCI to TBW for 2U1B1d olecranon fractures using human cadaver elbows.

Methods

A transverse olecranon fracture was simulated in eight matched pairs of cadaveric elbows. Matched pairs were used for comparison of TBW and CCI. Cyclic loading was performed at both 10 N and 500 N, with gap formation and load to failure recorded. Results: No significant difference in gap formation at 10 N (p > 0.3) or 500 N (p = 0.6), or load-to-failure (p=.00.41), was observed between the two groups.

Discussion

CCI fixation requires a smaller incision, is easy to perform, and involves low-profile implant that may reduce morbidity. Based on biomechanical properties that match the gold standard, continuous compression nitinol implants are an appropriate option for fixation of transverse olecranon fractures with potential advantages over tension band wiring.

Fracture Fixation Using Shape-Memory (Ninitol) Staples

Shape-memory alloy (SMA) staples are a recent innovation in fracture fixation. These staples have inherent compressive properties that create a stable fracture environment that promotes primary bone healing. They have been used successfully for osteotomies, arthrodesis, and fracture fixation. Understanding where SMA staple compression can be optimized and using proper indications are important for obtaining consistent success and minimizing failures. SMA staples are not a substitute for lag screw fixation or traditional plate and screw constructs.